Questions and Answers
What is the main characteristic of intermediate filaments?
What is the function of keratin filaments in epithelial cells?
What is the result of mutations in keratin-5 and -14?
What is the function of microtubules in cells?
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What is the role of GTP in microtubule polymerization?
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What is the function of dynein in microtubules?
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What is the function of actin filaments in muscle cells?
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What is the difference between G-actin and F-actin?
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What is the role of ATP in actin filament assembly?
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What is the function of centrosomes in microtubules?
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What is the role of formins in the actin cytoskeleton?
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Which protein is primarily responsible for stabilizing actin filaments in muscle tissue?
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What structural feature do microvilli provide for cells?
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What is the consequence of the loss of dystrophin in muscle cells?
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How do Arp2/3 complexes contribute to actin filament formation?
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What type of structural arrangement do actin bundles provide?
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What is the primary function of spectrin in cells?
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What is the outcome of actin-ADP dissociation?
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What is the primary function of formins in the actin cytoskeleton?
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What is the consequence of Duchenne Muscular Dystrophy?
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What is the primary function of tropomyosin?
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What is the purpose of microvilli in cells?
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Which type of filament is characterized as not being dynamic and providing structural support in cells?
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Which type of protein is predominantly found in the axons of neurons?
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What occurs to GTP-bound dimers when GTP is hydrolyzed?
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What is the primary role of kinesins in the cytoskeleton?
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What is the consequence of a mutation in keratin -5 and -14?
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Which characteristic distinguishes F-actin from G-actin?
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What is a key function of cilia in cellular structure?
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What do microtubules primarily contribute to during the cell cycle?
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Which property of microtubules allows for dynamic instability?
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What is the function of the basal lamina that intermediate filaments anchor to?
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Study Notes
Cytoskeleton Overview
- Composed of a 3-dimensional network of protein filaments within the cytoplasm.
- Adapts to form either dynamic or stable structures, crucial for cellular integrity and function.
Intermediate Filaments
- Non-dynamic structures providing structural support and reinforcement to cells.
- Provide scaffolding particularly in cells demanding structural integrity.
- Types include:
- Keratin filaments (Type I and II): Predominantly in epithelial cells.
- Vimentin and Vimentin-related filaments (Type III): Found in connective tissue, muscle, and glial cells.
- Neurofilaments (Type IV): Located in neuron axons.
- Nuclear lamina (Type V): Found within the nuclear envelope.
- Mutations in keratins can cause conditions like Epidermolysis Bullosa Simplex, resulting from mutations in Keratin -5 and -14, leading to fragile skin and blisters due to compromised anchoring to the basal lamina.
Microtubules
- Composed of rigid hollow rods that are highly dynamic.
- Serve multiple functions including:
- Intracellular transport, organization, and maintaining cell shape.
- Mitotic spindle formation during cell division (mitosis).
- Making up structures such as cilia and flagella.
- Structurally organized through tubulin heterodimers, binding in a head-to-tail manner with GTP binding.
- Exhibit dynamic instability, rapidly switching between polymerization and depolymerization, essential for cellular functions.
- Centrosomes act as organization centers where microtubules grow toward the plus end; they contain y-tubulin to initiate assembly.
- Motor proteins facilitate intracellular transport:
- Kinesins: Motor proteins that move towards the plus end.
- Dyneins: Motor proteins that move towards the minus end.
Actin Filaments (Microfilaments)
- Form thin, flexible structures regulated by actin-binding proteins with two forms: G-actin (globular) and F-actin (filamentous).
- G-actin exists in three isoforms, with different distributions among muscle and non-muscle cells.
- Functions include:
- Muscle contraction facilitated by myosin.
- Formation of cell surface extensions like microvilli for absorption and secretion.
- Providing tension and stabilization to the plasma membrane.
- Vital for cytokinesis during cell division.
- Elongation occurs through ATP-bound monomers adding to the plus end while ADP-bound monomers dissociate from the minus end.
- Actin structures can be bundled for projections (microvilli) or organized in networks for membrane support.
- Key regulatory proteins:
- Formins: Promote linear actin formation.
- Arp2/3 complexes: Initiate branched actin formation.
- Tropomyosin: Stabilizes actin filaments, especially in muscle cells.
- Spectrin: Provides cytoskeletal support in the cell cortex, crucial for red blood cell membranes.
- Dystrophin: Links actin to cell membranes in muscle cells; loss causes muscular dystrophies such as Duchenne Muscular Dystrophy.
Microvilli
- Actin-based structures that increase cell surface area to enhance nutrient absorption and secretion.
- Anchored to a terminal web, a dense region of the cytoskeleton providing stability.
Cytoskeleton Overview
- Composed of a 3-dimensional network of protein filaments within the cytoplasm.
- Adapts to form either dynamic or stable structures, crucial for cellular integrity and function.
Intermediate Filaments
- Non-dynamic structures providing structural support and reinforcement to cells.
- Provide scaffolding particularly in cells demanding structural integrity.
- Types include:
- Keratin filaments (Type I and II): Predominantly in epithelial cells.
- Vimentin and Vimentin-related filaments (Type III): Found in connective tissue, muscle, and glial cells.
- Neurofilaments (Type IV): Located in neuron axons.
- Nuclear lamina (Type V): Found within the nuclear envelope.
- Mutations in keratins can cause conditions like Epidermolysis Bullosa Simplex, resulting from mutations in Keratin -5 and -14, leading to fragile skin and blisters due to compromised anchoring to the basal lamina.
Microtubules
- Composed of rigid hollow rods that are highly dynamic.
- Serve multiple functions including:
- Intracellular transport, organization, and maintaining cell shape.
- Mitotic spindle formation during cell division (mitosis).
- Making up structures such as cilia and flagella.
- Structurally organized through tubulin heterodimers, binding in a head-to-tail manner with GTP binding.
- Exhibit dynamic instability, rapidly switching between polymerization and depolymerization, essential for cellular functions.
- Centrosomes act as organization centers where microtubules grow toward the plus end; they contain y-tubulin to initiate assembly.
- Motor proteins facilitate intracellular transport:
- Kinesins: Motor proteins that move towards the plus end.
- Dyneins: Motor proteins that move towards the minus end.
Actin Filaments (Microfilaments)
- Form thin, flexible structures regulated by actin-binding proteins with two forms: G-actin (globular) and F-actin (filamentous).
- G-actin exists in three isoforms, with different distributions among muscle and non-muscle cells.
- Functions include:
- Muscle contraction facilitated by myosin.
- Formation of cell surface extensions like microvilli for absorption and secretion.
- Providing tension and stabilization to the plasma membrane.
- Vital for cytokinesis during cell division.
- Elongation occurs through ATP-bound monomers adding to the plus end while ADP-bound monomers dissociate from the minus end.
- Actin structures can be bundled for projections (microvilli) or organized in networks for membrane support.
- Key regulatory proteins:
- Formins: Promote linear actin formation.
- Arp2/3 complexes: Initiate branched actin formation.
- Tropomyosin: Stabilizes actin filaments, especially in muscle cells.
- Spectrin: Provides cytoskeletal support in the cell cortex, crucial for red blood cell membranes.
- Dystrophin: Links actin to cell membranes in muscle cells; loss causes muscular dystrophies such as Duchenne Muscular Dystrophy.
Microvilli
- Actin-based structures that increase cell surface area to enhance nutrient absorption and secretion.
- Anchored to a terminal web, a dense region of the cytoskeleton providing stability.
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Description
Learn about the 3-dimensional network of proteins in the cytoplasm, including intermediate filaments, their characteristics, and types.
